Guizhou Xinzihong Pharmaceutic Adjuvant Co. Ltd.,
Dispersion and Hydration of Carbomer

Date of issue:2021/06/28Posted by: ZIHONG BIOTECH

Carbome is water soluble polymer, providing good suspending and thickening in personal care products, industrial fields such as alkaline battery gels, and being used as gelling agent in hydroalcoholic gels such as hand sanitizer gels, antibacterial gels. The gelling effect is activated in two stages, firstly the dispersion and hydration of the Carbomer, and secondly “neutralizing” the solution by the addition of chemicals which increase the pH. Neutralizing agents include triethanolamine, sodium hydroxide and potassium hydroxide.

The Problem

1)Carbomer polymer is generally supplied as a very light, low density powder. It tends to float when added to water, requiring vigorous agitation to be incorporated. This can cause dusting problems.

When added to the water, Carbomer polymer tends to form agglomerates which are not readily dispersed.

2)Some powders have poor flow properties, making controlled powder addition difficult.

3)While some grades display no significant increase in viscosity until neutralized, others start to thicken immediately, making addition of powder increasingly difficult.

4)Long mixing times are required to complete dispersion/hydration.

Aeration can create a persistent foam which may require chemical additives to disperse.

5)Entrained air is very difficult to remove, clouding clear gels and causing problems where packaging is filled by volume rather than weight.

Potential full yield is difficult to obtain with conventional agitation; many formulations contain unnecessarily high levels of Carbomer polymer to compensate for this.

Prolonged exposure to intense high shear can damage Carbomer polymer, reducing viscosity.

The Key Solution-Dispersion procedure

Dispersion is completed in a fraction of the time taken by conventional means, avoiding the risk of over shearing Carbomer polymer. Operation is described below.

1)To disperse Carbomer polymer completely, it should be slowly and carefully sprinkled to dispersion medium while the mix is stirred rapidly to avoid formation of lumps; extremely high shear rate mixer should be carefully employed to avoid viscosity loss.   

2)The ideal viscosity can be achieved at pH ranges of 5.0~10.0 when being neutralized; In a hydroalcoholic system, a correct neutralizer must be chosen carefully based on the amount of alcohol to be gelled.    

3) After neutralization, high-shear and lasting stirring should be avoided to keep stable thickening ability.  

4)Neutralization: In certain circumstances mixers can be used for the neutralization stage, depending on percentage and grade of Carbomer polymer. For high viscosity products, a low shear stirrer/scraper would be used.

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